For the playerMotor script, the changes basically boil down to adding a new run speed while on a horse, making it so running works while riding, and increasing jump height while on a horse and running.

Then there is the other script that deals with the transport modes where I had to create a separate animation transition timer when running and made it so the walking audio playes while running. If you want to see the code itself, I can send it to you over the weekend.

I also tried limiting turn speed while cantering and increasing the walking audio while cantering, but I couldn't figure out how to do either.

As for the canter speed being too high, I'd like to point out that this goes for all the movment options in the entire game, plus horses can move pretty crazy fast if they want to. The walking audio would also sound just like a canter would if it were louder and a little bit faster.

While cantering technically isn't part of classic, purists can ignore it by simply not pressing the sprint key while riding. This fits my definition of horizontal improvement that adds quality of life without substantially changing the base game experience.

I wouldn't mind seeing this in the base game, but purists (like myself, kind-of-sort-of) would probably be happier if the enhanced horseback riding features could be toggled on and off as a whole in the main menu, like with many of the other enhancements. I think this would be better game play wise, because those who would want to forgo feature could forget about it entirely, as opposed to having to be concerned with when they can or can't press their shift key. Just my two cents

Mod hooks into the Playermotor makes sense. There are many popular mods in other TES games that involve changing how the movement feels and behaves.

There are a lot of Vars in playermotor that would be fun to edit on the fly and have mod support for. I feel it would be great to edit lots of the players movement with spells or effects once that system is done.

So rewriting it to have mod support makes sense from that stand point.